Just a couple of observations about your post to Tammy (which shows a great deal of promise, btw<G>)
<%SNIP%>Finally we figured out that I was stretching my lips out to the
> sides much too far (which was difficult to spot because I don't have a
> particularly wide mouth). I am in the process of making a small
> change where I bring the corners of my mouth in, and hold them very
> tight, while keeping the rest of my embouchure supple. This creates a
> cushion for the mouthpiece.
Rather than keeping the corners of your mouth *very tight*, try to concentrate on merely holding the corners where they are when naturally relaxed (against the teeth), then drawing the remaining muscles IN, toward the center of your chops.... By keeping the corners tight, you may be compromising the seal in the center of your chops, thus weakening them(particularly the upper lip)...
> and an isometric excercise where I make a tight O with my
> mouth, place my fingers in the corners of my mouth, and push outward
> with my fingers while pulling inward with my lips.
Again, not always a good idea -- the key is to keep the corners firm, but not tight, and to avoid stretching them backward (toward your ears) at all (counterproductive to the development of the orbicularis oris as well as the buccinators...)
> A problem I'm left with still is that I don't have the control over my
> upper lip that I should, and it collapses out a little bit when I
> play, so that's another thing to check on.
Try this: watch yourself in the mirror, and try to roll your upper lip inwards (rather like the cartoon character who used to say *You dirty rat, I'm going to get you!*) but keep it on the OUTSIDE of your upper teeth... then bring the lower lip up, slightly OVER the top teeth to hold the upper lip in the rolled-in position...then do gentle squeaking noises (not like a regular buzz)...
This should help with developing the upper lip....Feel free to email
me back for a more detailled explanation...